BACKGROUND AND AIM: Ambulatory blood pressure monitoring (ABPM) is superior to conventional BP measurement in predicting outcome, with baseline 24-h, daytime and night-time absolute values, as well as relative nocturnal decline, as powerful determinants of prognosis. We aimed to evaluate ABPM estimates on the appearance of cardiovascular events and mortality in a cohort of high-risk treated hypertensive patients. METHODS AND RESULTS: A total of 2115 treated hypertensive patients with high or very high added risk were evaluated by means of office and 24-h ABPM. Cardiovascular events and mortality were assessed after a median follow-up of 4 years. Two hundred and sixty-eight patients (12.7%) experienced a primary event (nonfatal coronary or cerebrovascular event, heart failure hospitalization or cardiovascular death) and 114 died (45 from cardiovascular causes). In a multiple Cox regression model, and after adjusting for baseline cardiovascular risk and office BP, night-time SBP predicted cardiovascular events [hazard ratio for each SD increase: 1.45; 95% confidence interval (CI) 1.29-1.59]. Values above 130 mmHg increased the risk by 52% in comparison to values less than 115 mmHg. CONCLUSION: In addition to clinical determinants of cardiovascular risk and conventional BP, ABPM performed during treatment adds prognostic significance on the development of cardiovascular events in high-risk hypertensive patients. Among different ABPM-derived values, night-time SBP is the most potent predictor of outcome.